Dual-Band Antenna with Pattern and Polarization Diversity

This study proposes a pattern-diversity antenna with different radiation patterns at two different frequency bands (f₁ and f₂; f₁: broadside radiation pattern, f₂: conical radiation pattern). The proposed structure consists of a central circular antenna and two annular ring antennas, with each of the antennas having individual ports. Two of the ports (port 1 and port 3) exhibit orthogonal broadside radiation patterns at low bands, and the other two ports (port 1 and port 2) exhibit orthogonal conical radiation patterns at high bands. Thus, they have polarization diversity characteristics. To improve isolation between the ports, the inner part of the annular ring antennas is shorted by an array, and the outermost port is positioned orthogonal to the other ports. Using this configuration, the isolation values between the ports are -26.7 and -30.1 dB at the two frequency bands, respectively. Using the fabricated prototype, experimental results show that the proposed antenna achieves -10 dB bandwidths of 240 MHz (5.71-5.95 GHz) and 210 MHz (7.69-7.9 GHz) at f₁ and f₂, respectively.